This invention relates to methods of forming non-volatile resistance variable devices, and to methods of forming silver selenide comprising structures.
Semiconductor fabrication continues to strive to make individual electronic components smaller and smaller, resulting in ever denser integrated circuitry. One type of integrated circuitry comprises memory circuitry where information is stored in the form of binary data. The circuitry can be fabricated such that the data is volatile or non-volatile. Volatile storing memory devices result in loss of data when power is interrupted. Non-volatile memory circuitry retains the stored data even when power is interrupted.
This invention was principally motivated in making improvements to the design and operation of memory circuitry disclosed in U.S. Pat. Nos. 5,761,115; 5,896,312; 5,914,893; and 6,084,796 to Kozicki et al., which ultimately resulted from U.S. patent application Ser. No. 08/652,706, filed on May 30, 1996, disclosing what is referred to as a programmable metallization cell. Such a cell includes opposing electrodes having an insulating dielectric material received therebetween. Received within the dielectric material is a variable resistance material. The resistance of such material can be changed between low resistance and high resistance states. In its normal high resistance state, to perform a write operation, a voltage potential is applied to a certain one of the electrodes, with the other of the electrode being held at zero voltage or ground. The electrode having the voltage applied thereto functions as an anode, while the electrode held at zero or ground functions as a cathode. The nature of the resistance variable material is such that it undergoes a change at a certain applied voltage. With such voltage applied, a low resistance state is induced into the material such that electrical conduction can occur between the top and bottom electrodes.
Once this occurs, the low resistance state is retained when the voltage potentials are removed. Such can effectively result in the resistance -of the mass of resistance variable material between the electrodes dropping by a factor of 1,000. Such material can be returned to its highly resistive state by reversing the voltage potential between the anode and cathode. Again, the highly resistive state is maintained once the reverse voltage potentials are removed. Accordingly, such a device can, for example, function as a programmable memory cell of memory circuitry.
The preferred resistance variable material received between the electrodes typically and preferably comprises a chalcogenide material having metal ions diffused therein. One specific example includes one or more layers of germanium selenide having silver ions diffused therein and one or more layers of silver selenide having excess silver ions diffused therein. It is, however, difficult to form silver rich silver selenide.
While the invention was principally motivated in addressing the above issues, it is in no way so limited. The artisan will appreciate applicability of the invention in other aspects unrelated to the above issues, with the invention only being limited by the accompanying claims as literally worded without limiting reference to the specification, and as appropriately interpreted in accordance with the doctrine of equivalents.
The invention includes methods of forming non-volatile resistance variable devices, and methods of forming silver selenide comprising structures. In one implementation, a method of forming a non-volatile resistance variable device includes forming a patterned mass comprising elemental silver over a substrate. A layer comprising elemental selenium is formed over the substrate and including the patterned mass comprising elemental silver. The substrate is exposed to conditions effective to react only some of the elemental selenium with the elemental silver to form the patterned mass to comprise silver selenide. Unreacted elemental selenium is removed from the substrate. A first conductive electrode is provided in electrical connection with one portion of the patterned mass comprising silver selenide. A germanium selenide comprising material is provided in electrical connection with another portion of the patterned mass comprising silver selenide. A second conductive electrode is provided in electrical connection with the germanium selenide comprising material.
In one implementation, a method of forming a silver selenide comprising structure includes forming a substrate comprising a first outer portion and a second outer portion. The first outer portion comprises a patterned mass comprising elemental silver. The second outer portion does not comprise elemental silver. A layer comprising elemental selenium is formed over the first and second outer portions. The substrate is exposed to oxidizing conditions effective to both, a) react elemental selenium received over the first portion with elemental silver to form the patterned mass to comprise silver selenide, and b) remove elemental selenium of the layer over the second outer portion from the substrate.